The present invention relates to improvements in twist-off closures for bottles and other containers. The invention is particularly directed to tamper-evident twist-off closures which provide a readily observable indication that the container has previously been opened so that a user will be forewarned that the contents of the container may have been adulterated.
The present invention is particularly directed to improvements on the type of tamper-evident twist-off closures which include a plurality of tabs extending inwardly and upwardly from the closure skirt when the closure is in a sealed position in such a manner that the tabs are compressed against a ledge formed on the bottle to hold the cap, also referred to as a "crown", firmly in place. The closure is removed by initially rotating it with the result that the tab ends are shifted outwardly by cams formed on the bottle neck. Thereafter, the cap is lifted free of the bottle. In practice, once the cap has been removed, it cannot be re-locked on the bottle except with the aid of a relatively cumbersome and complicated machine which would not be available to someone seeking to surreptitiously open and re-seal a bottle. Various forms of caps and bottles of the general type described above are shown in Henning, U.S. Pat. No. 4,782,469 for TWIST-OFF BOTTLE CAPS, Henning, U.S. Pat. No. 5,263,600 for TAMPER-EVIDENT TWIST-OFF CLOSURE and the pending United States Patent Application of John C. Henning, Ser. No. 08/697,426 for TAMPER-EVIDENT CLOSURE SYSTEM.
More particularly, the closure shown in Henning, U.S. Pat. No. 4,782,469 includes a top wall, and a depending skirt having a plurality of narrow tabs extending from its lower edge. These tabs are generally rectangular and include a serrated outer edge. When the cap is applied to the bottle, the tabs are bent upwardly and inwardly to engage surfaces formed on the neck of the bottle below an endwise lip. These tabs are thus placed in compression, and thereby hold the cap tightly sealed against the upper lip of the bottleneck. The cap is removed by an initial twisting motion during which the tab ends are shifted outwardly, followed by a lifting motion to free the cap from the bottle.
The closure shown in Henning, U.S. Pat. No. 5,263,600 comprises a flat top, a depending ribbed skirt, and narrow tabs extending from the edge of the skirt. The tabs shown in this patent are generally rectangular with their outer edges being slightly asymmetrical relative to the centerline of the tab. These tabs are adapted to engage a shelf formed on a bottle with which the cap is used. These tabs are thus placed in compression, and function to hold the cap in position by compression in generally the same manner as the cap disclosed in U.S. Pat. No. 4,782,969.
Another cap construction incorporating generally rectangular tabs is shown in the co-pending patent application of John Henning for TAMPER-EVIDENT CLOSURE SYSTEM, Ser. No. 08/697,426. The tabs provided on the cap shown in that application extend from the edge of a skirt and have an outer edge which is slightly curved to facilitate its sliding engagement with a cooperating ledge on the bottle. The tabs are bent inwardly and upwardly to engage the ledge in such a manner that the tabs are compressed when the cap is in its closed, sealed position, and thereby function to hold the upper wall of the cap tightly against the upper lip of the bottle. The caps and bottles shown in Henning application Ser. No. 08/697,426 function extremely well when a cap is applied to the bottle. The caps are effective to retain internal bottle pressures in excess of the industry standard. The caps can be removed with a torque within an acceptable range and can be completely removed from the bottle in an easy manner. Moreover, once a cap has been removed, it cannot be replaced upon the bottle and resealed without the use of extremely cumbersome equipment. Consequently, when a user attempts to replace the cap, it remains relatively loose, providing clear and unmistakable evidence that the cap has previously been removed.
However, the cap shown in Henning application Ser. No. 08/697,426 for TAMPER-EVIDENT CLOSURE SYSTEM remains subject to one disadvantage in use. More particularly, the edges of the tabs and periphery of the skirt have shown a tendency to rust, rendering the bottle and cap somewhat unattractive. We have determined that this rusting is due to the accumulation of moisture on the inwardly bent tabs and inner surface of the cap skirt following the immersion of filled bottles in a sterilizing bath after the bottles have been filled and capped. As is well-known to those skilled in the art, after bottles have been filled with a beverage such as beer and the caps secured in place, the bottles are transported through a bath of hot liquid. Following this, air jets are directed against the caps to dry them and prevent rusting. We have determined that this drying procedure is not effective to prevent rusting of the prior art caps shown in the above-identified Henning application Ser. No. 08/697,426.